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From "Nick Bailey" <ni...@mailtrust.com>
Subject Re: Killing a zookeeper server
Date Tue, 12 Jan 2010 23:44:07 GMT
In my last email I failded to include a log line that may be revelent as well

2010-01-12 18:33:10,658 [QuorumPeer:/0.0.0.0:2181] (QuorumCnxManager) DEBUG - Queue size:
0
2010-01-12 18:33:10,659 [QuorumPeer:/0.0.0.0:2181] (FastLeaderElection) INFO  - Notification
time out: 6400

We see this line occur frequently and the timeout will graduatlly increase to 60000. It appears
that all of our servers that seem to be acting normally are experiencing the cpu issue I mentioned
earlier 'https://issues.apache.org/jira/browse/ZOOKEEPER-427'. Perhaps that is causing the
timeout in responding?

Also to answer your other questions Patrick, we aren't storing a large amount of data really
and network latency appears fine.

Thanks for the help,
Nick


-----Original Message-----
From: "Nick Bailey" <nicholas.bailey@rackspace.com>
Sent: Tuesday, January 12, 2010 6:03pm
To: zookeeper-user@hadoop.apache.org
Subject: Re: Killing a zookeeper server

12 was just to keep uniformity on our servers. Our clients are connecting from the same 12
servers.  Easily modifiable and perhaps we should look into changing that.


The logs just seem to indicate that the servers that claim to have no server running are continually
attempting to elect a leader.  A sample is provided below.  The initial exception is something
we see regularly in our logs and the debug and info lines following are simply repeating throughout
the log.


2010-01-12 17:55:02,269 [NIOServerCxn.Factory:2181] (NIOServerCnxn) WARN  - Exception causing
close of session 0x0 due to java.io.IOException: Read error
2010-01-12 17:55:02,269 [NIOServerCxn.Factory:2181] (NIOServerCnxn) DEBUG - IOException stack
trace
java.io.IOException: Read error
        at org.apache.zookeeper.server.NIOServerCnxn.doIO(NIOServerCnxn.java:295)
        at org.apache.zookeeper.server.NIOServerCnxn$Factory.run(NIOServerCnxn.java:162)
2010-01-12 17:55:02,269 [NIOServerCxn.Factory:2181] (NIOServerCnxn) INFO  - closing session:0x0
NIOServerCnxn: java.nio.channels.SocketChannel[connected local=/172.20.36.9:2181 remote=/172.20.36.9:50367]
2010-01-12 17:55:02,270 [NIOServerCxn.Factory:2181] (NIOServerCnxn) DEBUG - ignoring exception
during input shutdown
java.net.SocketException: Transport endpoint is not connected
        at sun.nio.ch.SocketChannelImpl.shutdown(Native Method)
        at sun.nio.ch.SocketChannelImpl.shutdownInput(SocketChannelImpl.java:640)
        at sun.nio.ch.SocketAdaptor.shutdownInput(SocketAdaptor.java:360)
        at org.apache.zookeeper.server.NIOServerCnxn.close(NIOServerCnxn.java:767)
        at org.apache.zookeeper.server.NIOServerCnxn.doIO(NIOServerCnxn.java:421)
        at org.apache.zookeeper.server.NIOServerCnxn$Factory.run(NIOServerCnxn.java:162)

2010-01-12 17:55:52,181 [QuorumPeer:/0.0.0.0:2181] (FastLeaderElection) INFO  - Adding vote
2010-01-12 17:55:52,181 [QuorumPeer:/0.0.0.0:2181] (FastLeaderElection) INFO  - Notification:
3, 30064826826, 1, 9, LOOKING, LOOKING, 9
2010-01-12 17:55:52,181 [QuorumPeer:/0.0.0.0:2181] (FastLeaderElection) DEBUG - id: 3, proposed
id: 3, zxid: 30064826826, proposed zxid: 30064826826
2010-01-12 17:55:52,181 [QuorumPeer:/0.0.0.0:2181] (FastLeaderElection) INFO  - Adding vote
2010-01-12 17:55:52,182 [QuorumPeer:/0.0.0.0:2181] (FastLeaderElection) INFO  - Notification:
3, 30064826826, 1, 9, LOOKING, LOOKING, 11
2010-01-12 17:55:52,182 [QuorumPeer:/0.0.0.0:2181] (FastLeaderElection) DEBUG - id: 3, proposed
id: 3, zxid: 30064826826, proposed zxid: 30064826826
2010-01-12 17:55:52,182 [QuorumPeer:/0.0.0.0:2181] (FastLeaderElection) INFO  - Adding vote
2010-01-12 17:55:52,183 [QuorumPeer:/0.0.0.0:2181] (FastLeaderElection) INFO  - Notification:
3, 30064826826, 1, 9, LOOKING, LOOKING, 12
2010-01-12 17:55:52,183 [QuorumPeer:/0.0.0.0:2181] (FastLeaderElection) DEBUG - id: 3, proposed
id: 3, zxid: 30064826826, proposed zxid: 30064826826
2010-01-12 17:55:52,183 [QuorumPeer:/0.0.0.0:2181] (FastLeaderElection) INFO  - Adding vote
2010-01-12 17:56:52,190 [WorkerReceiver Thread] (FastLeaderElection$Messenger$WorkerReceiver)
DEBUG - Receive new message.
2010-01-12 17:56:52,190 [WorkerReceiver Thread] (FastLeaderElection$Messenger$WorkerReceiver)
DEBUG - Receive new message.
2010-01-12 17:56:52,191 [QuorumPeer:/0.0.0.0:2181] (FastLeaderElection) INFO  - Notification:
3, 30064826826, 1, 9, LOOKING, LOOKING, 8
2010-01-12 17:56:52,191 [QuorumPeer:/0.0.0.0:2181] (FastLeaderElection) DEBUG - id: 3, proposed
id: 3, zxid: 30064826826, proposed zxid: 30064826826
2010-01-12 17:56:52,191 [QuorumPeer:/0.0.0.0:2181] (FastLeaderElection) INFO  - Adding vote
2010-01-12 17:56:52,192 [QuorumPeer:/0.0.0.0:2181] (FastLeaderElection) INFO  - Notification:
3, 30064826826, 1, 9, LOOKING, LOOKING, 12
2010-01-12 17:56:52,192 [QuorumPeer:/0.0.0.0:2181] (FastLeaderElection) DEBUG - id: 3, proposed
id: 3, zxid: 30064826826, proposed zxid: 30064826826
2010-01-12 17:56:52,192 [QuorumPeer:/0.0.0.0:2181] (FastLeaderElection) INFO  - Adding vote
2010-01-12 17:57:52,200 [WorkerReceiver Thread] (FastLeaderElection$Messenger$WorkerReceiver)
DEBUG - Receive new message.
2010-01-12 17:57:52,201 [WorkerReceiver Thread] (FastLeaderElection$Messenger$WorkerReceiver)
DEBUG - Receive new message.


-----Original Message-----
From: "Patrick Hunt" <phunt@apache.org>
Sent: Tuesday, January 12, 2010 5:40pm
To: zookeeper-user@hadoop.apache.org, nicholas.bailey@rackspace.com
Subject: Re: Killing a zookeeper server

12 servers? That's alot, if you dont' mind my asking why so many? 
Typically we recommend 5 - that way you can have one down for 
maintenance and still have a failure that doesn't bring down the cluster.

The "electing a leader" is probably the restarted machine attempting to 
re-join the ensemble (it should join as a follower if you have a leader 
already elected, given that it's xid is behind the existing leader.) 
Hard to tell though without the logs.

You might also be seeing the initLimit exceeded, is the data you are 
storing in ZK large? Or perhaps network connectivity is slow?
http://hadoop.apache.org/zookeeper/docs/current/zookeeperAdmin.html#sc_clusterOptions
again the logs would give some insight on this.


Patrick

Nick Bailey wrote:
> We are running zookeeper 3.1.0
> 
> Recently we noticed the cpu usage on our machines becoming
> increasingly high and we believe the cause is
> 
> https://issues.apache.org/jira/browse/ZOOKEEPER-427
> 
> However our solution when we noticed the problem was to kill the
> zookeeper process and restart it.
> 
> After doing that though it looks like the newly restarted zookeeper
> server is continually attempting to elect a leader even though one
> already exists.
> 
> The process responses with 'imok' when asked, but the stat command
> returns 'ZooKeeperServer not running'.
> 
> I belive that killing the current leader should trigger all servers
> to do an election and solve the problem, but I'm not sure. Should
> that be the course of action in this situation?
> 
> Also we have 12 servers, but 5 are currently not running according to
> stat.  So I guess this isn't a problem unless we lose another one.
> We have plans to upgrade zookeeper to solve the cpu issue but haven't
> been able to do that yet.
> 
> Any help appreciated, Nick Bailey
> 





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